Table 2.

Inhibition of oocyst formation by the SM1 peptide

Exp.	Peptide injected	Infected guts/total	Mean oocysts/gut (range)	% Inhibition	Transmission
1	—	5/5	34 (25–45)	—	ND
	SM1	0/5	0	100	ND
1a	—	9/10	9 (0–90)	—	ND
	SM1	0/10	0	100	ND
2	—	23/25	52 (0–140)	—	YES
	SM1	6/25	1 (0–9)	98	NO
3	—	15/15	77 (5–301)	—	YES
	SM1	6/15	2 (2–23)	96	NO
4	—	9/10	12 (0–29)	—	ND
	SM1	1/10	0 (0–2)	98	ND
5	—	14/15	21 (0–44)	—	YES
	Control	12/15	21 (0–130)	3	YES

For each experiment, An. stephensi were fed on an anesthetized P. berghei-infected mouse followed by injection into its tail vein of 200 μg of the SM1 or control peptide dissolved in 200 μl of saline. A second group of mosquitoes was fed on the mouse about 10 min after injection. Mosquitoes were kept at 21°C, and the no. of oocysts per midgut was determined on days 7 (Exp. 1), 10 (Exp. 1a), or 15 (Exps. 2–5). To determine their ability to transmit the parasite, 12–15 mosquitoes from Exps. 2, 3, and 5 were allowed to feed on naive mice (2 mice per experiment) on day 25. The infection status of these mice was determined by microscopic observation of blood smears every other day for a period of up to 1 month. A “YES” in the last column denotes that both mice were infected by the mosquitoes, and a “NO” denotes that no infection was detected for at least 1 month after mosquito feeding. ND, not determined.